In recent years, secondary batteries, which can be charged and discharged, have been widely used as an energy source for wireless mobile devices. In addition, the secondary batteries have attracted considerable attention as an energy source for electric vehicles (EV) and hybrid electric vehicles (HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuel.
Small-sized mobile devices use one or several battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a middle or large-sized battery module including a plurality of battery cells electrically connected to each other because high output and large capacity are necessary for the middle or large-sized devices.
Preferably, the middle or large-sized battery module is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell of the middle or large-sized battery module. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the weight of the pouch-shaped battery is small, and the manufacturing cost of the pouch-shaped battery is low.
For example, small-sized mobile devices, such as mobile phones, personal digital assistants (PDA), digital cameras, and laptop computers, use one or several small-sized, lightweight battery cells for each device according to the reduction in size and weight of the corresponding products. On the other hand, middle or large-sized devices, such as electric bicycles and hybrid electric vehicles, use a battery module (which may also be referred to as a “middle or large-sized battery pack”) having a plurality of battery cells electrically connected with each other because high output and large capacity are necessary for the middle or large-sized devices. The size and weight of the battery module is directly related to an accommodation space and power of the corresponding middle or large-sized device. For this reason, manufacturers are trying to manufacture small-sized, lightweight battery modules.
Conventionally, to this end, a plurality of battery modules is fixed as follows. The battery modules are stacked, fixing plates are mounted at the upper and lower ends of the battery module assembly to fix the battery modules, and the battery modules are fixed again in a frame. In this method, however, overall volume of the battery module assembly is increased. In addition, a conventional battery module cover is not provided to fix the battery module assembly but is provided as a structure dependent upon other fixing members. For this reason, it is necessary to provide an additional fixing device. Furthermore, the battery module cover is provided merely to protect terminal parts of the battery modules at which electrode leads are formed from the outside or to insulate the terminal parts of the battery modules.
Therefore, there is a high necessity for technology that is capable of fundamentally solving the above problems.